The present invention relates to a method of vibration reduction and apparatus for the same based on the technique of cross axis actuation.
Discussion of Prior Art
Cross axis actuators are used for the active control of vibration in various pieces of apparatus, in particular elongate members, and operate to isolate vibration to a particular part of an apparatus by actively deforming an element along which undesirable vibrations are transmitted.
Various approaches to the active control of vibration transmitted along elongate members are known. UK patent application, publication number 2229789 discloses the use of a plurality of elongate and rigid actuators which are attached in parallel across a length of elongate member. The elongate member has flanges anchored to it at two points along its length and the actuators are then attached to the flanges. The actuators are movable via control signals originating from sensors so as to cause small deformation in the member between the points of flange attachment. This results in vibrational energy being reflected back towards its source. By attaching six actuators it is possible to control all possible low frequency vibrations which the member undergos, that is, longitudinal (compressional), transverse and torsional vibrational modes. In this case each flange has three attachment points for the actuators the attachment points on each flange being positioned at an angle of 120.degree. to each other relative to the axis of the member. The relative attachment points on one flange to the other are offset by an angle of 60.degree. with respect to the axis of the member. Each flange attachment point serves to attach two actuators these actuators being attached to the two closest attachment points on the other flange.
This design is however rather complex and costly. It also occupies a significant volume within the region of the flanges and this may hamper fitment of the device and its maintenance.
There is therefore a requirement for a simplified approach to the design of cross axis actuators occupies less space in the region of attachment.